A trickster fey, Puck was banished from Avalon along with the rest of his race. Despite this, and despite Oberon's order that his children not interfere in mortal affairs, Puck continues to bypass these rules (as, admittedly, do others). Like other children of Oberon, such as Titania and Coyote, Puck developed an affinity for humans, and chose to remain with them on Earth rather than return to Avalon for the Gathering. Knowing that this could incur Oberon's wrath (indeed, Banshee's refusal of the same later resulted in a dire punishment for her), he planned to bribe Oberon with the Phoenix Gate in order to buy himself some more time, but he failed to get it from Goliath (By law, he could not take the Phoenix Gate by force, it had to be given to him.).
It was Puck that, during the show's run, cast the spell on Demona that made her turn human during the day, rather than turning to stone. Further, it was later revealed that Puck had played a far more central role in affairs than had previously been believed, when it was revealed that he had for many years been posing as Owen Burnett, the stiff and severely un-Puck-like aide to David Xanatos, who was in fact, based on Halcyon Renard's aide, Preston Vogel.
Before the beginning of the series, Puck, following the lead of Titania, had formed the identity of Owen Burnett by imitating Preston Vogel, the aide to Halcyon Renard. He had gone to work for Xanatos, whom he considered a trickster like himself, and eventually revealed his identity, offering a deal: a single wish from Puck, or a lifetime's loyal service from Owen, with no interference from Puck. Xanatos chose Owen, and the two have been inseparable ever since, so much so that Puck risked angering Oberon by remaining with Xanatos and missing the Gathering. He revealed himself when Oberon attempted to kidnap Xanatos's infant son, Alexander (also the grandson of Titania through his mother, Fox).
In the aftermath, Oberon decreed that Puck would remain with Xanatos to teach the young Alexander how to use his magical gift. However, he would be locked in the form of Owen when not training or protecting Alexander, and he was banished forever from Avalon. Puck himself reacted badly to this news (though Owen took it stoically, after he transformed back).
One night, while Xanatos and Fox went to dinner, Puck/Owen watched over Alexander and taught him his first magic lesson, soul switching. Disguising themselves as Goliath and Hudson, they bring the three souls inside of Coldstone (Coldstone himself, his love Desdemona, and the evil gargoyle Iago) into the bodies of Broadway, Angela and Brooklyn. Puck took on Coldstone's cyborg form while Alexander took over Lexington. They worked together to bring the souls inside Angela and Brooklyn to their new robotic bodies, Coldfire (Desdemona) and Coldsteel (Iago) respectively. This had been part of a plan made by Xanatos to make things up with Goliath. Once the souls went into their rightful bodies, Puck turns back to Owen and acted as if nothing had happened when the parents came home.
Puck was voiced by Brent Spiner, and Owen by Jeff Bennett.
Read more about this topic: Oberon's Children